From 31bdba07f6b262a489f71516a5978c3595fb4099 Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Wed, 7 Sep 2022 11:01:44 -0700 Subject: [PATCH] powerpc/64s/radix: don't need to broadcast IPI for radix pmd collapse flush commit bedf03416913d88c796288f9dca109a53608c745 upstream. The IPI broadcast is used to serialize against fast-GUP, but fast-GUP will move to use RCU instead of disabling local interrupts in fast-GUP. Using an IPI is the old-styled way of serializing against fast-GUP although it still works as expected now. And fast-GUP now fixed the potential race with THP collapse by checking whether PMD is changed or not. So IPI broadcast in radix pmd collapse flush is not necessary anymore. But it is still needed for hash TLB. Link: https://lkml.kernel.org/r/20220907180144.555485-2-shy828301@gmail.com Suggested-by: Aneesh Kumar K.V Signed-off-by: Yang Shi Acked-by: David Hildenbrand Acked-by: Peter Xu Cc: Christophe Leroy Cc: Hugh Dickins Cc: Jason Gunthorpe Cc: John Hubbard Cc: "Kirill A. Shutemov" Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/mm/book3s64/radix_pgtable.c | 9 --------- 1 file changed, 9 deletions(-) diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c index 795d18a84f55..a339cb5de5dd 100644 --- a/arch/powerpc/mm/book3s64/radix_pgtable.c +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c @@ -954,15 +954,6 @@ pmd_t radix__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long addre pmd = *pmdp; pmd_clear(pmdp); - /* - * pmdp collapse_flush need to ensure that there are no parallel gup - * walk after this call. This is needed so that we can have stable - * page ref count when collapsing a page. We don't allow a collapse page - * if we have gup taken on the page. We can ensure that by sending IPI - * because gup walk happens with IRQ disabled. - */ - serialize_against_pte_lookup(vma->vm_mm); - radix__flush_tlb_collapsed_pmd(vma->vm_mm, address); return pmd;